3. Session objective
At the end of this session we are expected to
define tonometry
Define intraocular presure
Define glaucoma
List the factor that influences IOP
List the type of tonometry
4. tonometry
• Tonometry is the standard tests of the eye
that is performed to determine the fluid
pressure in side the eye .
• Tonometer is an instrument used for
tonometry basically reply of deformity
specific area of the cornea by applying the
force which either flatten or indented cornea
5. INTRAOCULAR PRESSURE (IOP)
IOP is the fluid pressure inside the eye.
• It supports the wall of the eye ball and
maintains its optical shape.
• So,Maintenance and regulation of IOP have
critical role in ocular health
• Normal intraocular presure is a presure
Which does not leads to glaucomatous
damage of the optic nerve head
6. • normal range of pressures is from
10.5mmHg - 20.5 mmHg
• if IOP is greater than 21mmHg leads to
glaucoma
7. Glaucoma
• Glaucoma : A multifactorial disease usually
(but not always) associated with high IOP
• is a progressive condition of the eye which is
raised the intra ocular pressure occurs
progressively damage the optic nerve fibers
due to gradual loss of vision
8. • The definitive characteristics of glaucoma are
based on visual field loss or the appearance of
the disc or retinal NFL
• When the drainage angle of the eye suddenly
• becomes completely blocked, pressure builds
up rapidly, and this is called acute angle-
closure glaucoma.
9. Factors influencing IOP
There are different factors that affect IOP
1. the rate of formation of aqueous humor
2. The rate drainage of aqueous humor
3. The pressure in the episcleral veins
4. Hereditary
5. Age
6. sex
7. Anesthesia
10. Aqueous humour formation
• The aqueous humour is secreted by non-
pigmented epithelium of the ciliary processes
of ciliary body in the posterior chamber .
• The rate of formation is about 2–6 μL per
minute
• It flows constantly
11. Aqueous outflow
• The aqueous exits the eye either through the TM or in
the uveo scleral meshwork.
1. Trabecular outflow
• around 90% aqueous humor out flows by TM .
• Trabecular meshwork -> juxtacanalicular connective
tissue -> endothelial lining of schleme’s canal ->
collecting canal -> aqueous vein.
2 Uveo scleral out flow
minimum amount of aqueous humor (10%) out
flow by this.
12. • ciliary muscle -> superciliary space ->
suprachoroidal space -> sclera and other less
defined areas.
13. Uses of tonometry
It measures the pressure inside your eye.
is used to check for glaucoma
15. Direct Method
• A catheter is inserted into the anterior chamber of
the eye and the other end is connected to a
manometric device from which the pressure is
calculate.
• directly measure the pressure
• Can not be done on humans
16. Indirect Method
• based on eyes response to an applied force.
• It can be classified in to two ways
• Indentational and applanation
• Both indentation and applanation tonometers
effect a deformation of globe but the
magnitude varies
17. • Indentation tonometer is used to measure
the amount of deformation or indentation of
the globe in response to a standard weight
applied to the cornea or the area flattened by
a standard force.
• Applanation Tonometers are used to measure
force necessary to flatten a small, standard
area of cornea. The shape of corneal
deformation is simple flattening.
18. IOP is derived from a mathematical
calculation. They are two types on the basis
of variable that is measured.
Variable force: Area of cornea on applanation
held constant, force varies.
Variable area: Force applied to cornea held
constant, area varies.
.
19. • Applanation tonometry can be contact and
non contact tonometry
• Noncontact Tonometer: measures time
required to deform a standard area of corneal
surface.
• Contact Tonometers: it measures IOP by
deforming the globe and by apply the force .
